Thiel’s pins have a sharp point, knurled grip ring, and a pair of miniature o-rings (or some combination of those features.) However, generic dowel pins will work, available from McMaster-Carr or even a good hardware store. The diameter is 1/4" and the socket is 1" deep, so a pin should be at least 1.5" long. The three points define the base plane to eliminate rocking. A sonically important function is to drastically reduce recoil. The woofer acceleration against its air load creates enough rocking movement to smear the tweeter signal. You’ll hear cleaner highs with pins.
Beyond that there are issues around coupling or isolating from the floor and so forth and so on. A study in itself. But start with any pin and wade in.
Regarding serial numbers, it may not matter. The CS.5 had a relatively short life with about 1000 pairs made. I don’t think there are any variations. It, like the 1977 model 02 was a response to dealer interest in a $1K Thiel. I think it debuted at more like $1250. Thiel had demand for its core products and couldn't afford to keep making it. But it’s a real Thiel with a Jim Thiel tweeter and Jim Thiel woofer hardware. Like early Thiels, the woofer is a pulp/fiber cone which represents the largest cost savings. The woofer itself costs a little less, but the big savings is in the crossover. Pulp absorbs, distributes and damps cone resonances so that the crossover can be immensely simpler and therefore less expensive. Jim’s choice of aluminum diaphragms provides far wider bandwidth and transient integrity, but the various (well defined and predictable) resonances each require complementary circuits to eliminate them. Many high-end designers choose this soft-cone solution. Jim only nested there in the early days and revisited there for the CS.5. I find the product to be a fine, charming anomaly in Thiel’s line. I encourage anyone to snag one if it crosses your path.
